Beneficiation means and methods for autogenous grinding systems



1965 LE ROY c. FERGUSON ETAL 3,231,204

BENEFICIATION MEANS AND METHODS FOR AUTOGENOUS GRINDING SYSTEMS FiledOct. 5, 1962 2 Sheets-Sheet 1 INVENTORS L E ROY C. FERGUSON HARLOWEHARD/NEE- ATTORNEY (v Q 1966 LE ROY c. FERGUSON ETAL 3,23

BENEFICIATION MEANS AND METHODS FOR AUTOGENOUS GRINDING SYSTEMS Filed001:. 5, 1962 2 Sheets-Sheet 2 N mil I IIIJI T INVENTORS LE ROYC.FERGUSON W D! N G E United States Patent 3,231,204 BENEFICHATION MEANdAND METHQDS FOR AUTOGENOUS GRINDING SYSTEMS Le Roy C. Ferguson, Hibbing,Minn, and Harlowe Hardinge, York, Pa, assignors, by mesne assignments,to Koppers Company, Inc., Pittsburgh, Pa, a corporation of DelawareFiled Get. 5, 1962, Ser. No. 229,288 30 Claims. (Cl. 241-24) Thisinvention pertains to improvements in an autogenous grinding system inwhich the means and methods of operating the same is such as to causebeneficiation of at least one component of the material which is beingground autogenously in the mill and which material, preferably, issupplied to the mill in run-of-mine condition. More particularly, theinvention pertains to such a system, and method of operating the same,in which the beneficiation or treatment of the material undergoingreduction can be applied to an appreciable range of sizes of thematerial undergoing reduction, autogenously, in the mill.

Autogenous grinding or reduction of ore materials of .a friable nature,as the name implies, comprises the utilization of the materialundergoing reduction as its own size-reducing grinding media.Run-of-rnine material, which is the form in which the raw materialpreferably is utilized in accordance with the present invention,includes intermixed ranges of relatively coarse, medium and fine sizeranges of material. In accordance with the principles of the invention,it also is contemplated that such run-of-rnine material may have beensubjected to as least limited precrushing treatment in order to producea maximum coarse size of the range usually between 5 inches and 12inches diameter, these sizes not being intended as restrictive butmerely as somewhat illustrative. The addition of other media such asballs, usually in a small amount, is also contemplated. For acomprehensive discussion and explanation of autogenous grinding,attention is directed to co-pending application, S.N. 822,612, filedJune 24, 1959, in the name of Harlowe Hardinge, now Patent No.3,078,049, issued Feb. 19 1963. This invention is also contemplated foruse in either a so-called wet or dry circuit.

When operating a tumbling mill to perform autogenous grinding ofrun-of-mine material, it can be appreciated that various types andconditions of raw material will be fed to the mill over extensiveperiods of time, especially as the mill receives material from.different locations in a mine, for example, or from different mines,pits or quarries. Under such circumstances, it can be appreciatedfurther that the mill can contain an excessive amount of medium sizes ofmaterial, for example, over the proportion which is desired normally formost etfective autogenous grinding. For the sake of example only, and byno means to be considered as a size limitation, coarse material may beassumed to be between 6 inches and 3 inches in diameter, medium between3 inches and /2 inch, and fine /2 inch down to 35 mesh. In practicehowever, this invention encompasses a range of sizes after leaving themill in the order of approximately 5 inches down to approximately plus35 mesh.

Variations in size ranges depend upon the characteristics of thematerial being treated and objectives sought. Depending upon the type ofmaterial being handled by the mill at any given time, there usually is apreferred optimum proportion of intermixed size ranges of relativelycoarse, medium and fine materials. If for example the medium sizefraction of the mill charge exceeds the desired proportion of said sizerange to any substantial extent, the eficiency of the grinding operationbecomes impaired.

Not only is the etliciency of the grinding operation impaired if any ofsuch coarse, medium or fine size ranges becomes unduly excessive, butthe amount of work necessary to be performed by the mill is greater thanshould be necessary if the proportions of these various size ranges issuch as to effect optimum grinding conditions. It can be appreciatedstill further, that if an excessive fraction of medium sizes, forexample, exists in the mill and a substantial portion of such sizes areWaste matetrial, greater efficiency could be achieved if this wastematerial can be removed from the mill at a desired rate commensuratewith grinding efficiency, especially to decrease the burden upon themill. The same circumstances might pertain with respect to the coarsesize ranges, as well as to the finer size ranges. The finer size rangesin this regard are those generally still coarser than material which maybe classed as a finished product.

Under other autogenous grinding conditions, Where an ore is relativelyrich in the values desired to be obtained and further processed in oneway or another, and particularly if such medium size fractions, forexample, of the material are appreciable in amount, there is no needfurther to reduce in size such medium size fractions and if these mediumsize fractions, or at least a substantial portion thereof, are removedfrom the mill in this condition, the power requirements of the mill canbe decreased. Further, such richer and more concentrated forms of thevalue material frequently experience loss in recovery if reduced to toofine a size, where it is beneficial to remove such size fractions ofhigh value material from the mill with as little grinding thereof takingplace as possible.

One of the principal objects of the present invention is to provide botha mill system and methods of operating the same by which run-of-minematerial is subjected to autogenous grinding in a tumbling mill and asized portion of the load within the mill is removed therefrom andseparately treated, said sized portion which is considered as being toocoarse for proper beneficiation thereof is returned to the mill forfurther autogenous grinding, such further reduced material subsequentlybeing discharged from the mill in a smaller size range either forfurther treatment within the milling system or discharged as a finishedproduct.

Another object of the invention is to remove from the productsdischarged from an autogenous grinding mill a fraction thereof which istreated outside of the mill and a component, such as a desired sizedfraction of the thus treated material is then returned to the mill forfurther reduction in size, the means employed for treating the materialwhile outside of the mill preferably being capable of handling only alimited portion of the total amount of such size range of the materialnormally contained in the mill, yet eventually and effectively treatingsuch size ranges of material as it circulates through the autogenousmilling system, thereby reducing the cost and maintenance of such atreatment step.

A further object of the invention is to treat run-ofmine material havinga plurality of characteristics during the reduction stage thereof in anautogenous milling system and which material containsone or morecomponents having different grindability and hardness characteristics,such treatment comprising removing from the mill system, as soon aseconomically expedient during the milling process, a portion of thematerial respectively classifiable as tailings, concentrate, completelytreated material, or material to be designated for additional treatment,and appropriately treating that material which is removed from thesystem according to the values therein.

Still another object of the invention, ancillary to the foregoingfurther object, is to provide means to select a component undergoingtreatment for use as grinding media J in another grinding millingcircuit, and feeding such selected treated components to such lattermilling circuit.

A still further object of the invention, in conjunction with thetreatment of run-of-mine material as it is being reduced autogenously ina tumbling mill, is to remove a sized component, divide the samequantitatively, return one of said divided portions to the autogenousmill for further reduction, and treat another of said divided portionsto separate therefrom a component having desired characteristics, thedividing of said discharged size portions preferably being adjustable.

Still another object of the invention in conjunction with the foregoingis to provide various kinds of dividing mechanism at selected locationsin the mill system, all of said dividing mechanisms preferably being ofan adjustable nature and arranged to direct certain divided portions ofthe material to a selected treating apparatus to perform further desiredoperations upon the divided material before discharging the same fromthe mill system.

Details of the foregoing objects and of the invention, as well as otherobjects thereof, are set forth in the following specification andillustrated in the accompanying drawings comprising a part thereof.

In the drawings:

FIGS. 1 and 2 respectively are vertical sectional elevationsrespectively transverse and parallel to the axis of an autogenoustumbling mill and illustrate exemplary arrangements of run-of-minematerial therein as the same undergoes reduction during tumbling in themill, said mill having exemplary discharge means for certain size rangesof the material undergoing reduction.

FIG. 3 is a fragmentary vertical sectional elevation illustrating anembodiment of material segregating means mounted relative to thedischarge end of an autogenous grinding mill.

FIG. 4 is a fragmentary illustration of an end view of a mill dischargemeans and showing further treating units and dividing mechanism for themill system otherwise illustrated generally as in FIG. 3, the view inFIG. 4 at least partially being a vertical sectional end elevation ofthe mill discharge mechanism illustrated in FIG. 3.

FIG. 5 is a fragmentary illustration similar to the upper part of FIG. 4and comprises the mill discharge and taken on the line 5-5 of FIG. 3 andshowing another component adjacent the mill discharge end.

FIGS. 6 and 7 are fragmentary sectional elevations of two additionalembodiments of mill contour according to the invention.

Inasmuch as the mill system and process comprising the present inventionpertain principally to the employment of a tumbling mill of theautogenous grinding type for performing at least the initialsimultaneous reduction in size of all size ranges of run-of-minematerial, there is illustrated in FIGS. 1 and 2, an exemplary autogenousmill ill. For a compete description of the operation of this type ofmill and the process performed thereby, attention is directed toaforementioned co-pending application, S.N. 822,612, filed June 24,1959, now Patent No. 3,078,049, issued Feb. 19, 1963. For conveniencehowever, the following brief description of the operation of the milland the process performed thereby is set forth.

The autogenous mill It? comprises a drum 12 having opposite ends 14- and16 respectively provided with trunnions 18 and Eli which are rotatablysupported in suitable in suitable bearings, not shown, the mill beingrotated by conventiona power means, not shown. The trunnions 18 and Zllare hollow and respectively comprise inlet and exit means for the mill.A feed chute 22, which receives run-of-mine material from an appropriateconveyor or the like, discharges into the mill through trunnion 18,while exit trunnions 29 contains discharge cone 24-. The specific shapeof the mill is not a critical aspect of this invention, neither as tothe feed or discharge ends nor the specific proportions of the interiordimensions thereof.

The interior of the mill is provided with suitable lining means of aconventional nature and, overlying the same, are radial lifter bars 26which are carried by entrance end 14 of the mill, while preferablysectional type radial lifter bars 28 are connected detachably to theexit end 16 of the mill. In the preferred construction, the lifter bars28 secure grate sections 39 of segmental shape in spaced relationship tothe exit end 16 of the mill as thus shown in FIG. 2. An annulardischarge space 32 is formed between the exit end 16 of the mill and thegrate 3G to receive material which is capable of passing through theslots or other size-limiting opening means formed in the grate 3Q,exemplary arcuate grate slots being shown in FIG. 1. It should beunderstood, however, that such illustration is not to be regarded asrestrictive as to size arrangement or Width of said slots. Curved,generally radial lifting vanes or scoops 34, which are circumferentiallyspaced from each other, are provided in annular space 32 for purposes ofelevating the material discharged into the space, as the mill rotates,whereby when the elevated material rises above the axis of the mill, itwill fall by gravity into discharge cone 24 for exit from the mill.

One of the principal advantages of a mill of this type is that theradial lifter bars 25 and 28, in conjunction with the transverse lifterbars 36, will elevate the material to a substantial height within themill before the same cascades in a manner as illustrated in exemplaryform in MG. 1. The exemplary position of the material in the mill willbe somewhat as indicated by the irregular upper boundary line 38 thereofwhich is shown in FIG. 1. The mass of material undergoing reduction inthe mill will consist of various size ranges of relatively coarse,medium and fine material and the cascading of the material serves toreduce all size ranges of the same simultaneously.

As illustrated in exemplary manner in MG. 2, particularly in regard tothe coarse pieces 4t there is substantial transverse movement in agenerally axial direction Within the mill due to various elementstherein such as annular deflector rings 42, the sloping surfaces 44 ofthe peripheral liner of the mill as shown in FIG. '2, the convex natureof the ends 14 and 16 of the mill when such shape of mill is employed,the radial lifter bars 26 and 28 which also act at least somewhat asdeflector means. Such transverse movement of the material, comprisingall size ranges thereof, further facilitates the grinding actionafforded by the mill. A mill, such as shown in detail in FIG. 2, inwhich the diameter of the grinding zone is substantially greater thanthe axial length thereof, also aids in the mixing action which occurs insaid zone. For further details of the reasons and benefits of thischaracteristic of the grinding zone, attention is directed toaforementioned Patent No. 3,078,049.

Autogenous grinding of run-of-mine material, as indicated above, variesas to optimum elliciency in accordance with the available proportion ofrelatively coarse, medium and fine size ranges of the material,variations in the harness of the material, variations in the valuescontent within specific pieces or fragments of material, whether thegrinding operations are under wet or dry conditions, and various otherfactors well known to those familiar with autogenous grinding.

One purpose of the present invention is to counteract certaindisadvantageous conditions or circumstances in regard to grindingautogenously run-of-mine material, especially for purposes of insuringas far as possible optimum grinding conditions within the mill, andthereby effecting maximum economy from the standpoint of minimizing wearand consumption of power, coupled with maximum percentage of desiredproduct produced by the autogenous grinding mill and system.

Another important purpose is to increase recovery of the values in thematerial, as more fully described hereafter. In order to accomplishthese objectives, the present invention provides an autogenous grindingmill pound type of trommel, broadly indicated 46.

circuit and system in which the material progressively is reduced insize within the mill and all of the size ranges thereof which arecapable of passing through the size-limiting opening means of the grate30 will be discharged into the space 32 and from there, throughdischarge cone 24, into sizing means 56 shown in FIG. 4. In addition tothe material which passes through the openings of the grate 30 however,there also is provided, in accordance with the principles of the presentinvention, additional discharge openings 48 for permitting passage ofmedium size pieces which in the mineral dressing industry are referredto as pebbles or cobs, the number and placement of openings 43preferably being variable. These pebbles or cobs are designated 59, inexemplary manner, in FIG. 2 and certain of the subsequent figures andreferences.

The spaces 13 through which the pebbles 51) exit from the grinding zoneof the mill may comprise portions of the radial spaces between segmentaledges of the grate sections 31) for example. The extent and position ofthe discharge openings 48 is determined, for example, by the placementof the sections of the sectional type radial lifter bars. 28 andparticularly by the omission thereof at various locations within themill. One of the preferred positions for the discharge openings 4-8however is adjacent the periphery of the discharge end of the mill 1tand a number of such exemplary openings 48 are shown in FIG. 1. 'It willbe understood further, also,

that a certain amount of intermediate size ranges of material of alesser dimension than the maximum permitted to pass through the openings43 also will exit therethrough and be discharged from the mill but anysuch sizes of material so discharged will be classified and sizedappropriately by mechanisms and procedures described hereinafter. For amore complete description of this aspect of the treatment of thematerial, attention is directed to co-pending application, SN. 1291,filed January 8, 1960, in the name of Harlowe Hardinge, now Patent No.3,078,050, issued February 19, 1963.

As to the extent of the discharge openings 48, it will be seen that, atleast in accordance with the preferred condtions contemplated for themill, the openings 48 will be minor in proportion to the total dischargeareas adored by the openings in the grate sections 30, whereby only alimited proportion of such larger pieces or pebbles 50 will bedischarged from the grinding zone of the mill in comparison with thevolume of relatively fine size ranges of material discharged through theopenings of the grate 39.

The pebbles or cobs 5d which are discharged from the grinding zone ofthe mill may, for example, be of a size range between 3 inches and 1inch, Whereas another sized range material may, for example, be between1 inch and 10 mesh, the fine ranges of material being, for example,minus 10 mesh and finer. It will be understood however that thesedesignations are for purposes of illustration only, rather than beingrestrictive in nature and suitable variations are contemplated as hereinabove stated.

Several different types of material classifying and segregating meansare contemplated by the present invention, the numeral 12' being usedgenerically to designate all of such various embodiments thereof in theseveral figures of the drawings. While a trommel arrangement is hereillustrated, the use of separate sizing devices such as a multi-deckvibrating screen capable of making a number of size separations will bea preferred arrangement under many conditions.

Referring to FIG. 3, it will be seen that the discharge cone 24 of themill 11) has associated therewith a com- Concentric screens or bar-typetrommels 104 and 106 are connected to the exit end of mill 1% and arerotatable therewith. The inner trommel 1114 is relatively coarse, whilethe outer trommel 106 is relatively fine, the latter permitting thepassage therethrough of relatively fine size ranges of material 1138,which discharges into a conduit 110 and may be removed from the millsystem as a finished product if the nature of the material is suitable.As to an example of the size of the material 108, the maximum particlestherein may be in the range of minus 10 mesh or even 35 meshapproximately. This however is subject to variation due to the characterof material treated as well as product desired.

The classifying and segregating means 46, by reason of the use of coarsetrommel 104, is capable of separating from the exemplary coarse piecesor pebbles 50 an intermediate size range of material 112 which passesthrough trommel 104 but will not pass through sieve or trommel 106. Asto an example of the intermediate size material r 112, and subject tomodification as stated herein, it can be,

for example, plus 10 mesh and minus 1 inch, the same discharging into anappropriate chute and conduit 114, and subject to division by splitter116' as later explained.

The coarse fraction of material, comprising pebbles 5t}, discharges fromthe outer end of the inner trommel 104 into the upper end of chute 114which contains an other pivoted splitter 116 disposed between an innerwall 118 and the outer wall 120 of the chute 114, the inner wall 118merging with a pair of discharge chutes 122 and 124 which are best shownin FIG. 4.

The intermediate size material 112 is handled at this point similarly tothe pebble material 50 and is illustrated in FIG. 5 which is a section,viewed on the line 5-5 of FIG. 3, and in which the splitter 116' isindependent of splitter 116 shown in FIG. 4, although they are in thesame discharge hopper 114, but are separated by inner wall 118 intoseparate discharge chutes 122 and 124' as shown in FIG. 3.

The handling of materials of the type treated in the present inventionis best accomplished by limiting the size range of the material to betreated. The same method of treatment does not usually apply todiiferent size ranges, or the apparatus employed for the differentranges may require different adjustment for efiiciently handling onesize range from another, as is well known in the art. For this reasonprovision is made to divide the mill 10 product into different sizeranges for delivery thereof to different apparatus. An example of thismethod for dividing the size ranges into three components is exemplifiedby the multiple trommel means of FIG 3, and is further illustratedrelative to an overall mill system in FIGS. 4 and 5.

In accordance with the principles of the invention, it is principallythe so-called medium and near fine size ranges comprising for examplepebbles 50 and intermediate sizes 112 that are to be beneficiated ortreated in mill 1t) and the system included therewith. When a wide rangeof sizes such as exemplified above are to be treated, it is advisable inmany cases to divide the ranges into size limiting components. Two suchgeneral sizes of components are illustrated here but it is within thescope of this invention to add additional size limiting or segregatingmeans in a similar manner, if desired, or confine the operation to oneselected size range if advisable.

Referring to FIG. 4, a picking belt 64 is shown in the mill system toreceive the coarse size range of material comprising pebbles 50 and thelike, the same having been discharged thereonto from suitable,diagrammatically illustrated adjustably positionable guide mechanism125, or the like, to render the material suitable either for handpicking, or to transmit the same to a magnetic separator 66 of a pulleytype, for example, well known in the art. A pair of chutes or hoppers126 and 128 are shown in side-by-side relationship therein, each of thesame having a splitter 130 and 132 respectively, for purposes to bedescribed.

The guide mechanism may be positioned, for example, to direct the coarsefraction of material by appropriate means such as conduit 80, to a heavymedia separator 82. One example of this type of separator is illustratedin prior Patent No. 2,753,998, in the name of Harlowe Hardinge. Briefly,such seperator comprises a slowly rotating cylinder 82 containing liquid86 which usually is fortified by fine, heavy solids floating therein, ofsuch a consistency that the specific gravity of the liquid approximatesthat of the material to be separated, whereby the lighter portions ofsaid material tend to float and are discharged at outlet 88, while theheavier portions sink and are delivered to the opposite end it? byspiral flights 92 within the cylinder. Suitable buckets are providedwithin the end 9G which discharge into exit chute 94.

An auxiliary divider or splitter 132 is shown adjacent the exit chute 94of the separator 82, and is operable to direct the heavy media materialinto any one of a number of conduits or the like, to be describedhereinafter. The guide mechanism 125 also may be set to direct thecoarse range of material to the exemplary unit 36 comprisingsupplementary beneficiating or treating means of any one of a number ofdifferent types and from which the products may exit to one of severaldifferent possibilities to be described hereinafter.

Regarding discharge conduit 124, it preferably discharges into adividing or splitter mechanism 134 capable of directing the materialfrom conduit 124 into one of several channels, respectively for thefollowing exemplary purposes. The material discharged into conduits 122or 124 may, either with or without further beneficiation, be dischargedas finished products or they may, as required, either be returned to theautogenous mill 1t), directing to appropriate treating means in regardto conduit 122, or used, for example, as grinding media in an auxiliaryor supplemental size reduction device 136 of any appropriate type. Inthis latter regard, a tumbling type mill can be used in which the sizedpebbles 59 are suitable to serve as grinding media for reduction ofother material fed thereto which usually is considerably smaller in sizerange than said pebbles 50. If the size reduction device 136 is otherthan as described above, it may be, for example, a secondary crushing orcoarse grinding device useful for further beneficiation or treatmentsuch as directly reducing the size of the pebbles or coarser sizefractions either to render the values therein more readily accessibletobeneficiation or for tine grinding thereof or to producea productofsmaller usable size for return to mill 10 or other means.

In the exemplary mill system shown in FIG. 4, there also is an exemplaryreturn line 138 indicated as being directed to the entrance of the mill.10, even though such entrance is not shown in said figure. There alsois an exemplary conduit, feed belt or the like, 14% diagrammaticallyillustrated as leading to the entrance of the supplementary or auxiliarycrushing or grinding device 136. With these various return andconducting lines thus identified, a description of the further handlingof the products discharging from the various additional beneficiating ortreating means briefly referred to hereinabove, now will be set forth.

Considering first the material which is received from the classifyingand segregating means 46 and particularly the portion thereof which isdivided by splitter 116 so as to be directed into conduit 7124, thedivider or splitter 134 in the latter can be positioned either to directthe coarse fraction of material back to the mill 10, or to the auxiliaryor supplemental crushing or grinding device 136, or both,simultaneouslyv Appropriate positioning of splitter 134 may be adesirable procedure particularly when regulation of the quantitydelivered to crushing or grinding device 136 is desired. Said device 135may either be a tumbling mill, as above described, or a secondarycrushing or grinding unit for direct reduction of the pebbles tdelivered thereto. The product therefrom may either leave the millsystem at 14th or may be returned to the mill for further reduction insize by conveyor line 138 through appropriate positioning of guideaechanism 136. By this procedure, any excess accumulation of anintermediate size range in mill 1% can be eliminated and the capacity ofthe mill increased.

The material which is discharged into conduit 122 has va wider choice oftreatment than that which is illustrated :in exemplary manner as havingbeen discharged into conduit 124. For example, the directing blade 125may be set to discharge the material through conduit 62 onto pickingbelt 64 and, in the event the magnetic separator '66 is employed, someof the material, such as non-mag- :netic material for example, may bedischarged into chute or conduit 126 and, depending upon the setting ofthe :Splitter blade 1319, some or all of the material may be dischargedeither as waste or desired product, as indicated by the arrow 142, whilethat material which is discharged along the line of the exemplary arrow144, is

subjected to the action of an additional splitter which serves to directthe material into or divide the same between return line 138, whichcarries it to the entrance of :mill 10, or the conduit or feed belt Mt)which carries it fto auxiliary crushing or grinding device 13a fortreat- ;ment as heretofore described. The quantity delivered to:splitter 145 is adjustable by varying the position of splitter .130.

The magnetic material is carried into conduit 128 upon :release from themagnetic separator 65, whereupon it engages the divider or splitterblade 132, whereby some or all of the material may be discharged orremoved from the system, as indicated by the exemplary arrow 148, orsaid material may be directed to a further exemplary splitter 15%), fromwhich location the material can be directed in the same manner as thatdescribed for the nonmagnetic material indicated by conveyor lines 138and 140.

Regarding the heavy media products discharged from exit chute 94 of theseparator 82 and which products are subject to the splitter 132, it willbe seen that, depending upon the setting of such means 132, some or allof the material may be either discharged as waste or finished productaccording to arrow 152, or may selectively be directed either to theline 138 for return to the entrance of mill 10 or the line 14-0 fortransmission to the entrance of auxiliary crushing or grinding device13% or both.

The lighter segments of material discharged from the heavy mediaseparator 82, as indicated by the exemplary arrow extending from exit 38of said separator, may be handled similarly to the heavy or sinkmaterial as to discharge into splitter 154 and exit from the system at156, partial or total return to mill 10, or directing the same toauxiliary crushing or grind-ing device 136 via conveyor or conduit lines138 and/or 140.

Still a third possibility for the material in conduit 122 beingsubjected to a particular setting of the directing blade 125 comprisessetting the latter so as to direct the material along exemplary line 158to direct it to the exemplary supplementary beneficiating or treatingmeans 96 which can comprise any of a wide variety of means such asconcentrating tables, jigs, spirals, flotation apparatus, alternatemagnetic separators, as well as additional sizing and reduction meansincluding appropriate crushers or auxiliary mills. From this auxiliarybeneficiating or treating means 96, the product may be discharged, asindicated by the exemplary arrow 1%, as either a waste or finishedproduct for example, or a portion thereof may be returned to mill 14)through line 138, or another portion may be sent to a crushing orgrinding device 136, all as above described for the other beneficiationmeans.

The explanation of discharge conduit line 122 in H6. 4 also applies toconduit 122' of FIG. 5 which illustrates a finer size range of materialthan that of conduit 122 in FIG. 4. While guide means 125 of the systemin FIG. 4 may direct the product, in the size ranges produced in thecoarser separation circuit, to one of the beneficiation or treatingmeans, guide means 125 of the system in FIG. 5, which receives its splitmaterial from splitter '9 116', will direct its size range to anothertreating means as exemplified by the various means here described.

Guide means 125 or 125' preferably are not dividing or splitting meanssuch as splitters 116 or 116' of FIGS. 4 and 5 but are of the type madeto direct the entire amount received thereby to one of the appropriatebeneficiation, or treating means, unless special conditions prevail.This is a different action from the divider or splitter means in theother lines from discharge conduits 124 or 124', as illustrated bysplitters 116 and 134. This different action also applies to the othersplitters 130 and 146, which are in hte magnetic separator circuit, andlikewise to splitters 132 and 150, or splitters 132 and 154 in the heavymedia circuit. As for other beneficiation or treatment units 96, theoperation of splitters associated therewith for directing the products,as desired, is the same as described above, although not shown. Thesesplitter arrangements, as above described, if desired, direct all orpart of the material received thereby to one path or divide the quantityreceived according to the choice of the operator. Three paths generallyare available; exit from the system, return to mill 10, or delivery tothe crushing or grinding device 136.

Regarding the finer size ranges delivered from chute 110 of FIG. 3,these may leave the circuit entirely, or be treated therein, butordinarily the quantity is greater than that which is capable of beinghandled properly by the system contemplated here. One of the principaladvantages of the system comprising the present invention is theeconomical means of handling only portions of the various size rangesduring their period of retention in the circuit and as they are beingreduced in size. Thus the cost of the beneficiation apparatus is minimumand recovery of the values is increased. Such a procedure is unique byvirtue of the fact that all sizes are being reduced simultaneously inthe same system and such treatment is given to only relatively smallamounts of a given size range at any one time, yet the objectivesdesired are economically achieved.

As an example of the foregoing, if the larger size fractions dischargedfrom trommel 104 are in excess of the quantity desired to be treated bythe various means employed, said fractions may be returned to the mill.By this procedure an important step is accomplished in that thebeneficiation or treating devices need not be of a capacity. to handleall the product at one time. Such devices of lesser capacity can berelatively small and less costly than devices of larger capacity, yeteventually they handle the material prior to its being reduced so fineas to pass beyond the size range for which said beneficiation ortreatment step serves a useful purpose. This is particularly true in anautogeno-us grinding mill circuit handling run-of-rnine material wherethe tendency therein is to produce a relatively large percentage of asocalled medium size range in the mill charge. It follows, then, that bytreating a portion of the so-called medium size range by crushing orgrinding device 136, and returning the same to autogenous mill 1d, thepercentage of said so-cal led medium size range is controllable, withthe resultant beneficial eifect upon the autogenous grinding millcircuit.

In the mills illustrated in section in FIGS. 2 and 3, the ends areconical or sloping. Such contour is advantageous with certain materialsand under certain conditions, especially in regard to dischargecharacteristics inherent to a sloping grate. However, there are othercontours, especially of the discharge end of the mill, including thegrate attached thereto, which operate more advantageously with certainother kinds of material under other types of operating conditions. Twoexemplary embodiments of such other interior contours are illustrated inexemplary manner in FIGS. 6 and 7, both of which have in common thefeature of the grate being substantially perpendicular to the axis ofthe mill.

Referring first to the embodiment shown in FIG. 6, it

will be seen that the tumbling mill 10, which preferably is of theautogenous type, has sloping or conical opposite ends 14 and 16'. Theend 14' is protected by conventional lining material and is providedwith radial lifter bars 2% and an annular deflector ring 42". Theperiphery also is similar to that shown in FIG. 2 but the discharge end16 is provided with a grate 162 which is substantially perpendicular tothe axis of the mill and over the inner face of which preferably radiallifter bars 164 extend, the same serving to hold the grate 162 connectedto the exit end of the mill, if desired. The grate 162 extendssubstantially from the inner periphery of the mill toward the axis apredetermined extent, the inner periphery of the grate terminatingadjacent an annular deflector ring 166 which, like grate 162, is spacedin an axial direc tion from end wall 16' to provide an annular dischargespace 168 of greater relative capacity than the space 32 of theembodiment of FIG. 2 when mills of comparable dimensions are compared.Suitable spacer bars 170 serve to maintain said grate 162 and ring 166in operative spaced position relative to end 16'.

The deflector ring 1656 is spaced radially appreciably from the axis ofthe mill and also radially from the conical terminal member 172. Anannular interior wall member 174 extends between the perimeter of member172 and ring 166, the same preferably being made of conventionalabrasing resisting lining material and positioned relative to end 16' byspacer bars 170. Formed within the grate 162 are a limited number ofdischarge openings 176 of substantially greater size than the normaldischarge openings or slots in the grate 162, whereby a minor proportionof relative coarse size pieces 5t) and a small amount of fines andintermediate sizes of the material are discharged therethrough, saidpieces 50 comprising pebbles or cobs suitable for use as grinding mediain the mill 1d, if reintroduced thereto after removal, or in otherauxiliary or secondary mills. Such grin-ding media is similar, forexample, to the pebbles 50 discharged through openings 48 in theembodiments of FIGS. 2 and 3, but the openings 176 preferably are formeddirectly in the grate sections rather than being between the gratesections as in regard to openings 48.

One of the principal advantages of the perpendicular type grate 162 overthe sloping grate 30 is that grate 162 is much less subject to directimpact abrasion than grate 3i) and where material is particularlyabrasive, especially to the grate segments, grate 162 obviously is moreadvantageous than grate 30. In view of the position of the deflectorring 166 as compared with ring 42 of FIGS. 2 and 3, different deflectionwill occur relative to similar loads in the respective mills, wherebythe lateral movement of the material within the mill likewise isaffected, and depending upon the material, mill operationcharacteristics and the like, the position of ring 166 may offeradvantages over the position of ring 42 relative to grate 30 and themill axis in FIGS. 2 and 3, while the latter may offer advantages overthe positon of ring 166 of FIG. 6 in regard to other types of material,mill operation characteristics, and the like.

In the further embodiment of tumbling and preferably autogenous-typemill contour shown in FIG. 7, the end walls 14" and 16" preferably aresubstantially parallel and the same are lined with conventional liningmaterial and especially the wall 14" has radial lifter bars and adeflector ring carried thereby which are similar to the correspondingelements in the embodiments shown in FIGS. 2, 3 and 6. However, the endwall 16" is the exit end wall and it carries the grate 173 which notonlyis perpendicular to the axis of the mill but also is parallel to theexit end of the mill. The grate 178 also is spaced axially from end wall16" to provide exit space 180 into which material discharged from thegrinding zone of the mill through the grate openings is received priorto being elevated and completely discharged from the mill through theexit trunnion as in regard to the mill of FIGS. 2 and 3.

It will be'seen from FIG. 7 that the mill shown therein also is providedwith an annular, laterally extending expansion zone 132 between theperiphery of the mill and the outer periphery of grate 178, into whichfalling material may move laterally to expand, while when the materialis elevated during rotation of the mill and tumbles or cascades onto theload portion of the material in the lower portion of the mill, theannular deflecting ring causes further deflection over the afforded byring 42", on the opposite end of the mill, and additional deflectingring 1% adjacent the inner periphery of grate The latter ring and theperpendicular position of grate 178 offer advantages similar tocorresponding elements in the mill of FIG. 6 with respect to differentmaterials, mill operating conditions and the like. However, theexpansion zone as well as the parallel end walls of the mill of FIG. 7offer still other variations in operational characteristics which,especially in regard to some types of material and operating conditionswill offer advantages not possible with the other mill contoursillustrated and described herein. Conversely, these other contours ohcrmore advantages relative to still other materials ground under possiblydifferent mill conditions such as spec 1, wet or dry, and the like.

As in regard to the mill of FIG. 6, that in FIG. 7 also preferably has alimited number of discharge openings 138 therein of similar size andquantity, and for similar purposes, as openings 1% in the mill grate 162of FIG. 6, to discharge pebbles or cobs Openings 188 also are in thegrate per se.

For purposes of clarifying the intended meaning of certain terms usedhereinabove and in the appended claims, the following generaldefinitions are included:

Treating is intended to encompass size reduction and/or beneficiation ofthe material, either singly or in unison.

Size Reduction pertains to making size change only.

Beneficiation is generally considered the process of removing eitherpart or essentially all of the value material from the waste material,depending upon the characteristics of the material such as grainstructure, and usually requires size reduction at one or more sizeranges of the material so as to properly cause economic liberation ofmost of the waste material from the value material.

Value Material is relative in that it may and usually does contain somewaste material, hence the reason for size reduction of certain ores to arelatively fine degree, especially where the values are locked in so asto require fine division or grinding to render them accessible andliberate them. Other materials may be almost pure values, even in largersized com, oncnts, and still other ones have a mixture of thesecharacteristics.

Waste Material also is somewhat relative since it may be substantiallycompletely waste or contain a minor amount of values. Thus it is subjectto the same consideration as the above-described value material in thatit may require additional treatment at times such as size reduction and/or beneficiation, depending upon the character of the material.

From the foregoing, it will be seen that the various embodiments of millsystems, classifying and segregating means such as unit 46 in FIG. 4,together with the various directing and splitter arrangements andtreating means and units, are capable of handling selected size rangesof material. The present invention affords a relatively Wide variety ofvarious means and mechanisms, as well as processes produced thereby, foreffecting max imum eliiciency in the autogenous grinding mill 1t} andsystem associated therewith. One of the principal advantageous featuresof such systems is the provision of size limiting and adjustablypositionable discharge openings 48 through which a relatively wide rangeof sizes of materials may be discharged, in limited amounts, from theiii.

grinding zone of the mill so as to relieve the mill thereof and, inparticular, to remove relatively coarse fragments of value material fromthe mill system as soon as liberated from the waste material associatedtherewith, there- :by not only reducing reduction costs but, in manyinstances, greatly increasing the overall recovery of the value materialwhen the means and methods described are employed in conjunction with anautogenous mill treating a mix are of a wide range of sizes such asrun-ofmill ore.

While the invention has been described and illustrated in its severalpreferred embodiments, it should be understood that the invention is notto be limited to the precise details herein illustrated and describedsince the same may be carried out in other ways falling within the scopeof the invention as claimed.

No claim:

1.. A method of beneficiating run-of-mine friable mineral materialcomprising the steps of subjecting such material including relativelycoarse, medium and fine size ranges thereof to autogenous grindingWithin a mill to reduce all size ranges thereof, removing a portion ofse lected size ranges of said material larger than said fine size rangesfrom the mass of the material being reduced, subjecting said removedmaterial to treatment while not co-mingled with said mass comprising thesteps of classifying the same by screening into at least two generalsize ranges and beneficiating the coarsest size range'by subjecting thesame to magnetic separation to effect a separa: tion of material valuestherein from waste material, and returning to the mass of materialbeingreduced any part of said separated material requiring furtherreduction.

2. A method of beneficiating run-of-mine friable mineral materialcomprising the steps of subjecting such material including relativelycoarse, medium and time size ranges thereof to autogenous grindingwithin a mill to reduce all size ranges thereof, removing a portion ofse lected size ranges of said material larger than said fine size rangesfrom the mass of the material beingreduced, subjecting said removedmaterial to treatment while not co-mingled with said mass comprisingdividing the same into two components and subjecting one of saidcomponents to further reduction in size and subjecting the othercomponent to a beneficiation step to elfect a separation of Wastematerial from value material therein, subjecting one of the materialsseparated by said beneficiating step to additional size reduction, andreturning to the mass of material being reduced any part of saidseparated material requiring further reduction.

3. A method of beneficiating run-of-mine friable mineral materialcomprising the steps of subjecting such material including relativelycoarse, medium and fine size ranges thereof to autogenous grindingwithin a mill to educe all sizes ranges thereof, removing a portion ofselected size ranges of said material larger than said fine size rangesfrom the mass of the material being reduced, and subjecting said removedmaterial to treatment while not co-mingled with said mass comprisingetfecting a plurality of size range separations, subjecting each sizerange portion to division and, subsequently subjecting one dividedportion thereof to further reduction and subjecting the other dividedportion to beneficiation to produce fractions respectively comprisingvalue and waste material.

4s. The process according to claim 3 including the further step ofsubjecting said waste material fraction to further reduction in size.

5'. The process according to claim 3 including the further step ofsubjecting said value material fraction to further reduction in size.

6. A method of treating run-of-mine friable mineral material comprisingthe steps of subjecting such material including relatively coarse,medium and fine size ranges thereof'to autogenous grinding within a millto reduce all size ranges thereof, removing a portion of selected media.

:to feed run-of-mine material to tively medium size material means toreturn to the tumbling mill any desired portion size ranges of saidmaterial larger than said fine size ranges from the mass of the materialbeing reduced, subjecting said removed material to treatment while notcomingled with said mass and comprising the steps of classifying saidremove-d material by screening to separate it into at least two generalsize ranges, further treating the coarsest of said size ranges bydividin the same into two "components, subjecting one divided componentof said coarsest size ranges to a further beneficiating step, andbeneficiating the other divided component of said coarsest size rangesand returning one portion thereof to said mill to effect furtherautogenous reduction.

7. A method of treating run-of-mine friable mineral material comprisingthe steps of subjecting such material including relatively coarse,medium and fine size ranges thereof to autogenous grinding Within a millto reduce all size ranges thereof, removing a portion of selected sizeranges of said material larger than said fine size 'ranges from the massof the material being reduced, di-

viding said removed material into two components, sub- "jecting one ofsaid divided components of size ranges to be'neficiation treatment forthe separation thereof into at "leasttwo products, and directing one ofsaid products to an auxiliary grinding mill for use therein as grinding*8. A method of treating run-of-mine' friable mineral "materialcomprising the steps of subjecting such material including relativelycoasre, medium and fine size ranges thereof to autogenous grindingwithin a mill to reduce all size ranges thereof, removing a portion ofselected size ranges of said material larger than said fine size rangesfrom the mass of the material being reduced,

iary size reduction, and then subjecting the product of said auxiliarysize reduction to additional autogenous grinding to produce a product ofa desired size range.

' 9. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an autogenous tumbling mill having inlet andexit means therein, means said inlet means of said mill for simultaneousreduction of all sizes of such material including relatively coarse,medium and fine size ranges thereofjmeans to discharge from said exit ofsaid mill line and medium size ranges of material of predeterminedmaximum size, means to size the discharged material and segregate saidmaterial into relatively fine and relatively medium size ranges, meansto effect a selection of a portion of said medium size ranges ofmaterial, means to treat said selected portion of said relatobeneficiate the same, and

'of said beneficiated fraction of relatively medium material for furtherreduction in size.

10. The mill system according to claim 9 including additional meansoperable to return to the tumbling mill the relatively medium sizeranges of material which are not beneficiated.

11. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an autogenous tumbling mill having inlet andexit means therein,

means to feed run-of-mine material to said inlet means ofs'aid mill forsimultaneous reduction of all sizes of such material includingrelatively coarse, medium and fine size ranges thereof, means todischarge from said 'exit 'of said mill fine and medium size ranges ofmaterial f predetermined maximum size, means to size the dis- -chargedmaterial and segregate said material into relatively fine and relativelymedium size ranges, means to effect a selection of a portion of saidmedium sizeranges 'of material, means to treat 'a selected portion ofsaid relatively medium size material to beneficiate the same,

charge from said classify said discharged size ranges of materialsize-reduction means, and means to deliver said non-selected portion ofmedium size ranges of material to said size reduction means for furtherreduction treatment.

12. The mill system set forth in claim 9 further characterized by saidsizing means comprises screen means, and said mill system furtherincluding means to receive the sized ranges of material from said screenmeans, and said means to select a portion of said medium size ranges ofmaterial comprising dividing means adjustably positionable relative tosaid receiving means and operable to separate said desired portion ofmedium. size range of material from the material received by saidreceiving means and feed the same to said treating means forbenefieiating the same.

13. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an autogenous tumbling mill having inlet andexit means therein, means to feed run-of-mine material to said inletmeans of said mill for simultaneous reduction of all sizes of suchmaterial including relatively coarse, medium and fine size rangesthereof, diaphragm means adjacent said exit means having openingstherein to discharge therethrough from the grinding zone of said millfine size ranges of material of predetermined maximum size, saiddiaphragm also having a minor number of discharge opening means oflarger size than said aforementioned openings and of a total areasubstantially less than the total area of said aforementioned openingsalso to disgrinding zone a restricted amount of material ofpredetermined maximum size, means to classify said discharged sizeranges of material discharged from said mill and segregate said materialat least into relatively fine and relatively medium size ranges,adjustable means operable to receive said medium size ranges from saidsegregating means and divide the same, means to receive and treat adivided portion of said medium sized material to beneficiate the same,and means to effect a selection of any desired portion of saidbeneficiated portion of said medium sized material and return the sameto the tumbling mill for further reduction in size.

14. A mill system for autogenous grinding and treatment of friablemineral material comprising an autogenous tumbling mill having inlet andexit means therein,

means to feed run-of-rnine material to said inlet means of said mill forsimultaneous reduction of all sizes of such material includingrelatively coarse, medium and fine size ranges thereof, diaphragm meansadjacent said exit means having openings therein to dischargetherethrough from the grinding zone of said mill fine size ranges ofmaterial of predetermined maximum size, said diaphragm also having aminor number of discharge opening means of larger size than saidaforementioned openings and of a total area substantially less than thetotal area of said aforementioned openings also to dis charge from saidgrinding zone a restricted amount of material of predetermined maximumsize, means to discharged from said mill and segregate said material atleast into relatively fine and relatively medium size ranges, means todivide said medium size ranges into several desired portions, meansindependently of said autogenous mill operable to receive and furtherreduce the size of at least one of said desired portion of saidrelatively medium sized material, and means to return to said autogenousmill any desired portion of said further reduced medium sized portionfor still further reduction of the size thereof.

15. The mill system set forth in claim 9 further characterized by saidtreating means comprising a magnetic separator, and adjustable means toreceive separated fractions therefrom.

16. The mill system set forth in claim 9 further characterized by saidtreating means comprising a heavy assnaoa 17. A mill system forautogenous grinding and beneficiation of friable mineral materialcomprising an autogenous tumbling mill having inlet and exit meanstherein, means to feed run-of-mine material to said inlet means of saidmill for simultaneous reduction of all sizes of such material includingrelatively coarse, medium and line size ranges thereof, means todischarge from said exit of said mill relatively fine and a restrictedamount of a relatively medium sized range of material, means to receiveand classify the discharged size ranges of material from the grindingzone of the mill and segregate said material at least into relativelyfine and relatively medium size ranges, means to effect a selection of adesired fraction of said classified medium size ranges of material,means to treat at least said selected fraction of said sized mediumrange of material to beneficiate the same, an auxiliary autogenous mill,and means to feed a desired portion of said beneficiated relativelymedium size fraction of material to said auxiliary autogenous mill toserve as grinding media therefor.

18. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an auto genous tumbling mill having inletand exit means therein, means to feed run-of-mine material to said inletmeans of said mill for simultaneous reduction of all sizes of suchmaterial including relatively coarse, medium and fine size rangesthereof, means to discharge from said exit of said mill time and mediumsize ranges of material of predetermined maximum size, means to size thedischarged material and segregate said material into relatively fine andrelatively medium size ranges, means to divide said medium size materialinto two portions, means to treat one of said divided portions of saidrelatively medium size material to beneficiate the same, and means toreceive and further reduce in size the other divided portion of saidrelatively medium size material.

19. The mill system according to claim 18 further including an auxiliarysize-reduction means, and material directing means communicating withsaid dividing means to receive said other divided portion of saidrelatively medium size material and operable selectively to direct saidother divided portion either to said autogenous tumbling mill or to saidauxiliary size-reduction means for further reduction in size.

20. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an autogenous tumbling mill, means to feedrun-of-rnine material thereto for simultaneous reduction of all sizes ofsuch material including relatively coarse, medium and fine size rangesthereof, means to discharge from said mill medium and fine sizes of apredetermined maximum size and a minor restricted proportion of coarsesize range, screening means positioned to receive said materialdischarged from said mill, said screening means being arranged andoperable to separate said fine and medium size ranges from each otherand including means otherwise arranged and operable to separate saidrestricted proportion of coarse material from said medium size ranges,means to divide said medium sized material into separated portions,beneficiating means, means to direct one of said divided portions ofmedium sized material to said beneficiating means for treatment thereby,additional size-reducing means, and means selectively operable to directthe other divided portion of medium sized material to said autogenousmill or to additional size-reducing means for further reduction in size.

21. The mill system according to claim 20 further including directingmeans positioned to receive said one divided portion after beingbeneficiated and operable selectively to direct any desired portion ofsaid beneficiated material to said autogenous mill or to said additionalsizereducing means for further reduction.

22. A mill system for autogenous grinding and beneficiation of friablemineral material comprising an autogenous tumbling mill, means to feedrun-of-mine material thereto for simultaneous reduction of all sizes ofsuch material including relatively coarse, medium and fine size rangesthereof, means to discharge from said mill medium and fine sizes of apredetermined maximum size and a minor restricted proportion of coarsesize range, screening means positioned to receive said materialdischarged from said mill, said screening means being arranged andoperable to separate said fine and medium size ranges from each otherand being otherwise arranged and operable to separate said restrictedproportion of coarse material from said medium size ranges, means todivide said coarse material into separated portions, beneficiatingmeans, means to direct one of said divided portions of coarse materialto said beneficiating means for treatment thereby, additional sizereducing means, and means selectively operable to direct the otherdivided portion of said coarse material to said mill or to saidauxiliary size,- reducing means for further reduction in size.

23. The mill system according to claim 22 further including directingmeans positioned to receive said one divided portion after beingbeneficiated and operable selectively to direct any desired portion ofsaid beneficiated material to said mill or to said additional auxiliarysizereducing means for further reduction in size.

24. The mill system according to claim 22 further including additionaldividing means positioned to receive and divide said medium size rangesof material into separated portions, additional beneficiating means, andmeans to direct one of said divided portions of medium size ranges ofmaterial to said additional beneficiating means for treatment thereby.

25. The mill system according to claim 24 additionally including meansselectively operable to direct the other divided portion of medium sizeranges of material to said mill or to said additional size-reducingmeans for further reduction in size.

26. A method of treating run-of-mine friable mineral material in a sizereducing system comprising the steps of subjecting such material toautogenous grinding Within a mill to reduce all size ranges thereof,removing from the system a fine size range, selecting and removing fromthe mill a size range of said material larger than said fine size rangefrom the mass of the material being reduced, subjecting a controlledportion of said selected material to a size reduction step While notco-mingled with said mass in said mill, and returning said portion tosaid mass for further reduction thereof.

27. A mill system for autogenous grinding and treatment of friablematerial comprising an autogenous tumbling mill having inlet and exitmeans therein, means to feed run-of-mine material to said inlet means ofsaid mill for simultaneous reduction of all sizes of such material,means to discharge from said exit of said mill fine and medium sizeranges of material of predetermined maximum size, means to size thedischarged material and segregate said material into relatively fine andrelatively medium size ranges, adjustable means to select a portion ofsaid medium size ranges of material, means to reduce the size of saidselected portion of said relatively medium size material, and means forreturning the remaining portion of said medium size ranges of materialback to the grinding zone of the autogenous grinding mill.

28. The mill system set forth in claim 27 further characterized by thediameter of the internal grinding zone of the mill being substantiallygreater than the axial length thereof.

29. The mill system set forth in claim 27 further characterized by thesizing means being capable of varying the size of the medium size rangeas discharged from the grinding zone of the mill substantiallyindependently of the fine sizes, said sizing means comprising aperturemeans Within said mill.

30. The mill system set forth in claim 27 further including means tovary the quantity of medium size ranges References Cited by the ExaminerUNITED STATES PATENTS Spitzer et a1.

Broadley 241-80 Pontoppidan 241-79 X Weinig 241- X Ladoo et a1.

Horsfield 241-26 X Erickson 241-20 Dowesett 241-80 X Fern et a1. 241-76X Lawver 241-79 1/1960 Hardinge 241-19 8/1960 Wales 241- 11/1960 Weston241- X 2/1963 Hardinge 241-26 2/1963 Hardinge 241-78 X 3/1963 Heckett241-79 X 4/1963 Lukas 241-24 References Cited by the Applicant 7/1923Ewing et 211.

OTHER REFERENCES German application, 1,033,604, July 10, 1958.

15 ROBERT C. RIORDON, Primary Examiner. I. SPENCER OVERHOLSER, Examiner.

1. A METHOD OF BENEFICIATING RUN-OF-MINE FRIABLE MINERAL MATERIALCOMPRISING THE STEPS OF SUBJECTING SUCH MATERIAL INCLUDING RELATIVELYCOARSE, MEDIUM AND FINE SIZE RANGES THEREOF TO AUTOGENOUS GRINDINGWITHIN A MILL TO REDUCE ALL SIZE RANGES THERE OF, REMOVING A PORTION OFSELECTED SIZE RANGES OF SAID MATERIAL LARGER THAN SAID FINE SIZE RANGESFROM THE MASS OF THE MATERIAL BEING REDUCED, SUBJECTING SAID REMOVEDMATERIAL TO TREATMENT WHILE NOT CO-MINGLED WITH SAID MASS COMPRISING THESTEPS OF CLASSIFYING THE SAME BY SCREENING INTO AT LEAST TWO GENERALSIZE RANGES AND BENEFICIATING THE COARSEST SIZE RANGE BY SUBJECTING THESAME TO MAGNETIC SEPARATION TO EFFECT A SEPARATION OF MATERIAL VALUESTHEREIN FROM WASTE MATERIAL, AND RETURNING TO THE MASS OF MATERIAL BEINGREDUCED ANY PART OF SAID SEPARATED MATERIAL REQUIRING FURTHER REDUCTION.